System and method for behavior based control of an autonomous vehicle

ABSTRACT

System and method for behavior based control of an autonomous vehicle. Actuators (e.g., linkages) manipulate input devices (e.g., articulation controls and drive controls, such as a throttle lever, steering gear, tie rods, throttle, brake, accelerator, or transmission shifter) to direct the operation of the vehicle. Behaviors that characterize the operational mode of the vehicle are associated with the actuators. The behaviors include action sets ranked by priority, and the action sets include alternative actions that the vehicle can take to accomplish its task. The alternative actions are ranked by preference, and an arbiter selects the action to be performed and, optionally, modified.

FIELD OF THE INVENTION

The present invention relates generally to control of unmanned groundvehicles and, more specifically, to variations in the control ofunmanned ground vehicles in response to environmental changes oroperator intervention.

BACKGROUND OF THE INVENTION

Vehicles and equipment that operate with little or no operatorintervention are desirable partly because they remove the operator fromharm's way in dangerous applications and because they offer direct laborcost savings in commercial applications. In many instances, this limitedintervention is exemplified by an operator removed from the confines ofthe vehicle itself and placed in a location with a remote control devicethat interfaces with and controls the vehicle. In this configuration,however, the operator typically must directly and continuously monitorthe vehicle and its surrounding environment, adjusting, for example,vehicle speed and direction, as needed. In particular, when a task iscomplex, the operator must carefully monitor the vehicle or equipment tothe point where any simplification of the operator's tasks is negated bythe high level of concentration required to ensure the vehicle avoidsobstacles, hazards, and other terrain features in its path, therebypreventing accidents. This requires considerable effort by the operator,a significant investment in skilled operator training, and places severelimitations on mission duration and objectives.

In a typical environment, a vehicle can encounter any number ofunforeseen hazards. A vehicle can also create or exacerbate a hazard. Ineither case, there is the potential that the vehicle may endangerpersons or property. Accordingly, an operator generally pays particularattention to events that may result in dangerous conditions. Thisadditional safety concern negatively affects mission effectivenessbecause it directs the operator's attention away from the particulars ofthe task the vehicle is performing. Additionally, an operator may becomeoverwhelmed by the degree of oversight and attention required and mayfail to recognize one or more obstacles or hazards in the path of thevehicle, potentially resulting in an accident.

From the foregoing, it is apparent that there is a direct need forefficient, autonomous control of a vehicle or equipment that relievesthe operator of most, if not all, of operational oversight. The vehicleor equipment needs to accomplish its assigned tasks while compensatingfor the environment in an autonomous fashion but still be responsive tothe attempts by an operator to assume control. The vehicle must alsoensure the safety of the its surroundings.

SUMMARY OF THE INVENTION

The present invention provides a system and method for behavior basedcontrol of an autonomous vehicle. While operating autonomously, thevehicle is aware of its surroundings, particularly the location andcharacter of terrain features that may be obstacles. Because theseterrain features can represent hazards to the vehicle, the vehiclepreferably compensates by altering its trajectory or movement.

The invention features a method for the behavior based control of anautonomous vehicle where several behaviors are associated with theactuators that manipulate input devices that direct the vehicle. Aninput device may be an operator input device that directs at least partof the vehicle (e.g., one or more of a steering wheel, handle, brakepedal, accelerator, or throttle). The input device also may be a devicedirectly or indirectly connecting the operator input device to acontrolled element (i.e., the object in the autonomous vehicleultimately controlled by the operator input device). For example, theoperator input device may be a throttle, and the input device may be thethrottle body. Although a human operator typically accesses andmanipulates the operator input device, the input device need not beaccessible or operable by the human operator.

A behavior is a program that proposes an action based on sensor data,operator input, or mission goals. Actions are typically grouped intoaction sets, and the action sets are generally prioritized. The actionswithin an action set are termed “alternative actions,” and eachalternative action generally has a corresponding preference. Thepreferences allow for the ranking of the alternative actions.

Multiple behaviors continuously propose actions to an arbiter. Thearbiter continuously decides which behavior is expressed based on aweighted set of goals. The arbiter selects the action set with thehighest priority, and also selects the alternative action from withinthe selected action set with the highest corresponding preference. Abehavior based system can include many behaviors and multiple arbiters,and multiple arbiters can be associated with an actuator. Multiplearbiters associated with an actuator are sometimes referred to as“stacked arbiters.” An actuator is typically a servo-system andtransmission in physical contact with the existing input devices in thevehicle.

In some embodiments, the behaviors characterize the operational mode ofthe vehicle. These modes include; manned operation, remote unmannedtele-operation, assisted remote tele-operation, and autonomous unmannedoperation. In the manned operation mode a vehicle operator sits in thevehicle cockpit and drives the vehicle using its traditional commandinput devices (e.g. steering wheel, brake, accelerator, throttle, etc.).In the remote unmanned tele-operation mode a dismounted operator or anoperator in a chase vehicle drives the unmanned vehicle from a safestand off distance through a portable operator control unit that allowsthe operator to directly command the vehicle. In the assisted remotetele-operation mode, the dismounted operator can engage “assistivebehaviors” that facilitate mission execution. These assistive behaviorsuse the vehicles sensors, control system, and perception andlocalization subsystems to add short-term, safe, self-navigationfunctionality to the vehicle. Examples of assisted behaviors includeactive obstacle avoidance, circling in place and deploying payloadsbased on sensor input. Such an assist allows the operator to focus moreon the mission and less on the continuous demand of driving. In theautonomous mode, the vehicle uses an arbitrated behavior based techniqueto perform a tactically significant mission. Examples of such missionsinclude following a moving object at a fixed distance and travellingthrough a pre-recorded set of fixed GPS waypoints while activelyperforming obstacle avoidance. Each mode can include a set ofalternative behaviors that the vehicle can take to accomplish its task.In some embodiments, the alternative behaviors are ranked by priority orpreference and an arbiter selects the behavior to be performed. Thebehavior can then operate the corresponding vehicle control accordingly.

In some embodiments, the behaviors include trajectory sets and, infurther embodiments, the behavior includes adjusting the translationalvelocity, or rotational velocity, or both, of the autonomous vehicle,typically in response to data received from sensors or a map of terrainfeatures located around the vehicle.

Another aspect of the invention includes a system for behavior basedoperation of an autonomous vehicle that includes a controller, such as amicroprocessor or microcontroller, that provides the host environmentfor the multiple resident behavior programs and the arbiter program and,in response to the behaviors, operates one or more vehicle controlsusing actuators. The controller also communicates with one or morelocalization or perception sensors, and using one or more localizationand perception behaviors builds a vehicle centric terrain feature map.The controller runs the behavior system and specifies the actions to beperformed.

Other aspects and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, illustrating the principles of theinvention by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the presentinvention, as well as the invention itself, will be more fullyunderstood from the following description of various embodiments, whenread together with the accompanying drawings, in which:

FIG. 1 is a flowchart depicting a method for interruptible autonomouscontrol of a vehicle in accordance with an embodiment of the invention;

FIG. 2 is a block diagram depicting a system for interruptibleautonomous control of a vehicle in accordance with an embodiment of theinvention;

FIG. 3 is a flow chart depicting a method for processing a safety signalin an autonomous vehicle in accordance with an embodiment of theinvention;

FIG. 4 is a block diagram depicting a system for processing a safetysignal in an autonomous vehicle in accordance with an embodiment of theinvention;

FIG. 5 is a flowchart depicting a method for tracking a terrain featureby an autonomous vehicle in accordance with an embodiment of theinvention;

FIG. 6 is a block diagram depicting a system for tracking a terrainfeature by an autonomous vehicle in accordance with an embodiment of theinvention;

FIG. 7 is a flowchart depicting a method for the behavior based controlof an autonomous vehicle in accordance with an embodiment of theinvention;

FIG. 8 is a block diagram depicting a system for the behavior basedcontrol of an autonomous vehicle in accordance with an embodiment of theinvention;

FIG. 9 is a flowchart depicting a method for multi-modal control of avehicle in accordance with an embodiment of the invention; and

FIG. 10 is a block diagram depicting a system for multi-modal control ofa vehicle in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

As shown in the drawings for the purposes of illustration, the inventionmay be embodied in systems and methods for controlling vehicles, wherethe systems and methods compensate, with little or no operatorintervention, for changes in the environment around the vehicle.Embodiments of the invention enhance overall mission effectiveness andoperating safety.

In brief overview, FIG. 1 is a flowchart depicting a method 100 forinterruptible autonomous control of a vehicle in accordance with anembodiment of the invention. The method includes a step of firstidentifying one or more input devices in the vehicle (STEP 104). Aninput device may be an operator input device that directs at least partof the vehicle (e.g., one or more of a steering wheel, handle, brakepedal, accelerator, or throttle). The input device also may be a devicedirectly or indirectly connecting the operator input device to acontrolled element (i.e., the object in the autonomous vehicleultimately controlled by the operator input device). For example, theoperator input device can be a drive control. A drive control generallyincludes a throttle, brake, or accelerator, or any combination thereof.In other embodiments, the operator input device can be an articulationcontrol. An articulation control generally operates equipment attachedto the vehicle. This can include, for example, a control used tomanipulate a blade on a bulldozer, or a tilling apparatus on a tractor.Although a human operator typically accesses and manipulates theoperator input device, the input device need not be accessible oroperable by the human operator.

Next, the method 100 includes the step of providing one or more controlpolicies (STEP 106) corresponding to the input device. Generally, thecontrol policies determine the manner in which the vehicle operatesincluding, for example, whether the control of the vehicle will beautonomous, manual, or a combination thereof. In addition to theidentification of the input devices and control policies, the inventionalso includes the step of providing one or more actuators (STEP 108)associated with one or more input devices. The actuator is typically anelectro-mechanical device that manipulates the input device.Manipulation occurs by, for example, pushing, pulling, or turning theinput device, or by any combination thereof. A result of this is theautonomous control of the vehicle. Furthermore, in an embodiment of theinvention, the actuators still allow manual operation of the vehicle. Inother words, the presence of actuators in the vehicle does not precludemanual operation of the corresponding input devices. In someembodiments, a linkage or other mechanical transmission associates theactuator with the corresponding input device. A linkage is generallyapparatus that facilitates a connection or association between the inputdevice and the actuator. A typical linkage is a lever and pivot joint, atypical transmission is a rack and pinion device.

Following the identification of the input device (STEP 104), providingthe control policy (STEP 106), and providing the actuator (STEP 108), anembodiment of the invention provides autonomous control of a vehicle(STEP 102). Autonomous control allows a vehicle to be operated accordingto programmed instructions, with little or no operator intervention.Autonomous control typically includes “intelligence” that allows thevehicle to compensate for unforeseen events, such as an encounter with aterrain feature such as an obstacle. During autonomous control, anembodiment of the invention monitors the input devices and actuators fora disassociation therebetween (STEP 110). The disassociation isgenerally any break in a physical connection between the input deviceand the corresponding actuator. For example, the input device can be anoperator input device, such as an accelerator pedal, connected to anactuator that is a rack and pinion device. An operator can disassociatethe accelerator from the actuator by, for example, depressing theaccelerator. In some embodiments, the disassociation is detected bymeasuring the response of one or more sensors (STEP 112).

On detection of the disassociation (STEP 110), autonomous control isinterrupted in favor of other operational modes (STEP 116). For example,on detection of the disassociation, a system according to an embodimentof the invention initiates a vehicle shutdown sequence (STEP 114). Thiscan occur when, for example, the vehicle operator depresses a “panicbutton,” thereby allowing a controlled, safe shutdown of the vehicle.

In other embodiments, following detection of the disassociation (STEP110), autonomous control is interrupted (STEP 116) to allow manualcontrol (STEP 118). One example of this occurs when an operator wants toincrease temporarily the speed of a vehicle that is under autonomouscontrol. By depressing the accelerator, a system according to anembodiment of the invention relinquishes the autonomous control andallows the vehicle to accelerate according to the operator's preference.

After the interruption of autonomous control (STEP 116), differentembodiments of the invention detect a restored association between theinput device and the corresponding actuator (STEP 120). Thereassociation is typically entails the reestablishment of the physicalconnection between the input device and the corresponding actuator. Thisis generally detected by measuring the response of one or more sensors(STEP 122). In the example discussed above, the reassociation wouldoccur when the operator stops depressing the accelerator, therebyallowing the accelerator to reconnect with its actuator.

Following the reassociation, one embodiment of the invention establishesa revised vehicle control (STEP 124). The nature of the revised vehiclecontrol depends on the control policy provided (STEP 106). For example,in some embodiments, the revised vehicle control includes returning toautonomous control (STEP 102). This can occur immediately. In otherembodiments, returning to autonomous control (STEP 102) occurs after adelay (STEP 126). In different embodiments, the operator must firstintervene (STEP 130) before the vehicle returns to autonomous control(STEP 102). This configuration provides, for example, a safety featurewhere the operator must confirm that returning the vehicle to autonomouscontrol is reasonable and proper.

In certain embodiments, the control policy provided (STEP 106) includespreventing the vehicle from further autonomous control after theinterruption of autonomous control (STEP 116). For example, in atractor, an operator may want to stop the tilling apparatus and ensurethat it can not restart automatically. When a system according to anembodiment of the invention detects a disassociation between the tillercontrol and the corresponding actuator (STEP 110), typically because theoperator has manipulated the tiller control thereby disrupting thephysical connection between the tiller control and the correspondingactuator, autonomous control is interrupted (STEP 116). Embodiments ofthe invention would detect the restored association between the tillercontrol and the corresponding actuator (STEP 120) when, for example, theoperator released the tiller control, and then attempt to establish arevised vehicle control (STEP 124). Nevertheless, in this example, thecontrol policy provided (STEP 106), includes inhibiting furtherautonomous control (STEP 128). Stated differently, in some embodiments,the control policy dictates, on a input device-by-input device basis,what actions are appropriate following the interruption of autonomouscontrol. For certain input devices, such as the accelerator examplediscussed above, reestablishment of autonomous control is proper. Forother input devices, however, safety or other considerations dictatethat autonomous control not be restored.

FIG. 2 is a block diagram that depicts a system 200 for interruptibleautonomous control of a vehicle in accordance with an embodiment of theinvention. The system 200 typically includes one or more input devices202. An input device may be an operator input device that directs atleast part of the vehicle (e.g., one or more of a steering wheel,handle, brake pedal, accelerator, or throttle). The input device alsomay be a device directly or indirectly connecting the operator inputdevice to a controlled element (i.e., the object in the autonomousvehicle ultimately controlled by the operator input device). Forexample, the operator input device can be a drive control 204. A drivecontrol generally includes a throttle 206, brake 208, accelerator 210,or transmission shifter 211, or any combination thereof. A typical inputdevice 202 is a throttle body (not depicted), which is typicallyconnected to the throttle 206. Other example input devices 202 include asteering gear (not depicted) and tie rods (not depicted). In otherembodiments, the input device can include an articulation control 212.

The system 200 also includes one or more control policies 214corresponding to the input device 202. Generally, the control policy 214determines the manner in which the vehicle will operate, typicallyallowing for vehicle control under autonomous or manual conditions, or acombination thereof. The system 200 also includes one or more actuators216 associated with the one or more input devices 202. Typically, theactuator 216 includes an electro-mechanical device that drives the inputdevice 202. In one embodiment of the invention, the actuator 216includes one or more linkages or other mechanical transmissions 218.Generally, a linkage provides the association (e.g., physicalconnection) between an actuator 216 and the associated input device 202.A typical linkage is a lever and pivot joint, a typical transmission isa rack and pinion device.

In some embodiments of the invention, the system 200 includes one ormore detectors 220. The detector 220 discerns a disassociation betweenthe input device 202 and the actuators 216. Typically the disassociationincludes a break in contact or communication between the input device202 and its associated actuator 216. By way of example, such contact orcommunication may be physical, or via electrical or mechanicalcommunication, or any combination thereof. In another embodiment, adisassociation can include a separation between the input device 202 andthe associated actuator 216. In an alternative embodiment, the detector220 includes a proximity sensor 222, or a strain gauge 224, or both.After a disassociation between the input device 202 and the actuator 216has occurred, the detector 220 discerns a restored association betweenthe same. Generally, a restored association includes a renewed contactor communication between the input device 202 and its correspondingactuator 216. For example, such renewed contact or communication may bephysical, or via electrical or mechanical communication, or anycombination thereof.

The system 200 also includes one or more controllers 226 that, in someembodiments, are in communication with the actuators 216 and thedetectors 220. The controller 226 is capable of interrupting autonomouscontrol (STEP 116). The controller 226 executes a vehicle controlprogram 228, based at least in part on the control policies 214. In someembodiments, the controller 226 is a microprocessor. In otherembodiments, the controller 226 is a microcontroller.

In another embodiment, the vehicle control program 228 includes a modulethat provides for autonomous vehicle control 230. In another embodiment,the vehicle control program 228 includes a predetermined time delaymodule 232. In some embodiments, the vehicle control program 228includes an inhibitor module 234 that prevents autonomous vehiclecontrol. The inhibitor module 234 prevents autonomous vehicle control inthe absence of operator intervention (STEP 130).

Other embodiments of a system according to the invention include ashutdown sequence 236 managed by the controller 226. The shutdownsequence is based at least in part on the disassociation between theinput device 202 and its corresponding actuator 216. Typically, theshutdown sequence 236 includes a controlled stop of the vehicle inresponse to an emergency.

In brief overview, FIG. 3 is a flowchart depicting a method 300 forprocessing a safety signal in an autonomous vehicle in accordance withan embodiment of the invention. The method includes a step of firstidentifying one or more input devices in the vehicle (STEP 104). Aninput device may be an operator input device that directs at least partof the vehicle (e.g., one or more of a steering wheel, handle, brakepedal, accelerator, or throttle). The input device also may be a devicedirectly or indirectly connecting the operator input device to acontrolled element (i.e., the object in the autonomous vehicleultimately controlled by the operator input device). Generally, anoperator input device may be linked to or associated with an inputdevice to control the operation of all or part of the vehicle. Forexample, the input device can be a drive control. A drive controlgenerally includes a throttle, brake, or accelerator, or any combinationthereof. In other embodiments, the input device can be an articulationcontrol. An articulation control generally operates equipment attachedto the vehicle. This can include, for example, a control used tomanipulate a blade on a bulldozer, or a tilling apparatus on a tractor.

Next, the method 300 includes the step of providing one or more controlpolicies (STEP 106) corresponding to the input device. Generally, thecontrol policies determine the manner in which the vehicle operates,including, for example, whether the control of the vehicle will beautonomous, manual, or a combination thereof. In addition to theidentification of the input devices and control policies, the inventionalso includes the step of providing one or more actuators (STEP 108)associated one or more input devices. The actuator is typically anelectro-mechanical device that manipulates the input device.Manipulation occurs by, for example, pushing, pulling, or turning theinput device, or by any combination thereof. A result of this is theautonomous control of the vehicle. Furthermore, in an embodiment of theinvention, the manipulation of the input device by the actuators allowfor a controlled shutdown of the vehicle.

Following the identification of the input device (STEP 104), providingthe control policy (STEP 106), and providing the actuator (STEP 108), anembodiment of the invention includes the step of providing one or morecontrollers (STEP 302). A controller allows the vehicle to be operatedaccording to programmed instructions and, in some embodiments, withlittle or no operator intervention. A controller typically includes“intelligence” that allows for any combination of manual or autonomouscontrol of the vehicle. Furthermore, in at least one embodiment of theinvention, the controller detects and processes a safety signal, and inanother embodiment, the controller detects and processes a stop signaland a non-stop signal (i.e., a signal that indicates a “stop” has notbeen commanded). The non-stop signal is also represented by the absenceof the stop signal.

Next, the method includes the step of providing a first communicationlink between the controller and each corresponding actuator (STEP 304).In one embodiment of the invention, the first communication linkincludes a network connection between the controller and eachcorresponding actuator. The network connection can be part of, forexample, a local area network or wide area network. It can be a wired orwireless connection, and may provide access to the Internet. Typically,the network connection is part of a real-time control network thatadheres to an industry standard (e.g., the “CAN” open standard).Generally, the first communication link connects, (for example, via anetwork) the actuators so the vehicle can change modes of operation. Inone embodiment, the change in modes of operation is in response to thesafety signal. For example, the safety signal may dictate that thevehicle stop moving, so the change in modes would include one or moreactuators associated with the drive control manipulating the drivecontrol to stop the vehicle. Generally, the first communication link isany electrical, mechanical, wired, wireless, or any combination thereof,communication between the controller and corresponding actuators. Inaddition to the first communication link, the method also includes thestep of providing a second communication link between each correspondingactuator (STEP 306). In an embodiment of the invention, the secondcommunication link includes one or more current loops. A current loop istypically a continuous wired connection with electrical current flowingthrough it. Components associated with the current loop detect ormeasure this electrical current, doing so directly or indirectly (e.g.,by measuring a voltage drop across a resistive element). A variance ofthe current from an expected value (e.g., interruption of the current)is generally a signal that the current loop conveys. In embodiments ofthe invention, the second communication link conveys a manual modesignal, an autonomous mode signal, or any combination thereof. In yetanother embodiment, the second communication link conveys a stop signal,non-stop signal (i.e., the absence of the stop signal), or anycombination thereof. Typically, the second communication link isconfigured as a serial hardwire connection between the actuators. Inother words, the second communication link progresses from one actuatorto the next sequentially, forming a ring.

Next, an embodiment of the invention includes the step of transmittingthe safety signal to each of the plurality of actuators via the firstcommunication link, the second communication link, or any combinationthereof (STEP 308). Generally, this communication may occur in anymanner in which data is transmitted from one actuator to another. Forexample, the communication may be electrical, mechanical, wired,wireless, or any combination thereof. In some embodiments, the safetysignal is transmitted in response to operator intervention (STEP 310).For example, an operator may depress an “emergency stop” button thattriggers the transmission of the safety signal (STEP 308). In otherembodiments, the safety signal is transmitted in response to the outputof at least one sensor (STEP 312). This can occur if a sensor measuresan instability in the vehicle, such as if the vehicle was about tooverturn. The controller provided (STEP 302) interprets the output ofthe sensor, determines an unsafe condition has developed, and triggersthe transmission of the safety signal (STEP 308).

In some embodiments, the vehicle enters a safe mode of operation on thedetection of an emergency or safety signal that is communicated betweenthe controller and each corresponding actuator via the firstcommunication link. In other embodiments, the vehicle automaticallyenters a safe mode of operation on the detection of an emergency orsafety signal that is communicated between corresponding actuators viathe second communication link. Furthermore, in some embodiments there isredundant transmission of the safety signal via both the firstcommunication link and second communication link. In any case, thesafety signal is transmitted to the corresponding actuators, whichrespond accordingly.

Following the transmission of the safety signal (STEP 308) an embodimentof the invention includes the step of manipulating the input device(STEP 314) based at least in part on the corresponding control policyand the safety signal. Generally, the manipulation of the input device(STEP 314) may be the physical movement of an input device by itscorresponding actuator in response to the safety signal to effect achange in vehicle mode of operation. In one embodiment of the invention,the manipulation of the input device (STEP 314) includes initiating ashutdown sequence (STEP 316) to shut down the vehicle. This can occur,for example, in emergency situations where the proper course of actionis a controlled, safe, shutdown of the vehicle.

In some embodiments, the safety signal is transmitted in response tooutput of the sensors. For example, a sensor may indicate that thevehicle, (for example, a tractor) may be on a collision course with aterrain feature that is an obstacle, such as a rock or ditch. Thisindication may be in the form of a safety signal. Based at least in parton the safety signal, the controller will become informed of theobstacle, incorporate the proper control policy, and communicate withthe associated actuators via the first communication link. The actuatorswill then manipulate the corresponding input devices accordingly inorder to avoid the obstacle. Such manipulation may result in shuttingdown the vehicle, or generally a change in the mode of operation of thevehicle in response in part to the safety signal, thus preventing anaccident.

As another example, the tilling apparatus in a tractor may need to bestopped because the tractor has reached the end of the plot of land thatneeds to be tilled. In this situation, it may become necessary for thetractor to remain running or in motion but for the tilling apparatus tostop or shut down. Here, the safety signal may be generated throughoperator intervention, such as disengaging the input device of thetilling apparatus from its associated actuator or, in some embodiments,via a sensor indicating the end of tillable land. In the first scenario,operator intervention causes the transmission of the safety signal, insome embodiments, by breaking the current loop in the secondcommunication link, and, in accordance with the corresponding controlpolicy, the tractor will continue to run while the actuatorcorresponding to the tiller input device is disengaged or shut off. Inthe second scenario, the sensor data is processed by the controller andtransmitted in accordance with the corresponding control policy, in someembodiments, by the first communication link over a network to theactuator corresponding to the tiller input device such that the tilleris disengaged or shut off while the remaining actuators continue toengage their respective input devices. In some embodiments, a result isa change in the vehicle mode of operation in response to the processingof the safety signal.

There are other embodiments in which the safety signal is transmitted inresponse to operator intervention. For example, on the detection of anemergency or safety signal, which may occur when an operator interruptsautonomous operation by depressing the brake, the current loop (anembodiment of the second communication link) is broken, causing an opencircuit, and acting as a transmission of the safety signal to thecorresponding actuators by the second communication link. The inputdevice will then be manipulated accordingly based at least in part onthe safety signal and the control policy corresponding to thatparticular input device. The safety signal and corresponding controlpolicy causes the vehicle to operate in manual mode, or autonomous mode,or any combination thereof. Furthermore, in the same example, the safetysignal could also be a stop signal, non-stop signal, or any combinationthereof, to control the vehicle mode of operation. The vehicle willdetect this occurrence and produce an autonomous mode signal, or in thealternative, enter a controlled shutdown mode, thus responding to andprocessing the safety signal.

In yet other embodiments, the safety signal is transmitted via both thefirst communication link and the second communication link, thuscreating a redundant method for processing the safety signal. Generally,this ensures that the safety signal will be processed properly in theevent one of the two communication links becomes inoperative. Forexample, as previously discussed, if an operator becomes aware of anobstacle and depresses the brake, the resulting safety signal will betransmitted serially via the second communication link to all associatedactuators. Additionally, a sensor may detect the same obstacle and send,via the controller and in accordance with the proper control policy, thesafety signal to the appropriate actuators via the first communicationlink to avoid the obstacle. Thus, in the event that one communicationlink fails, the other communication link will still process a safetysignal.

FIG. 4 is a block diagram that depicts a system 400 for processing asafety signal in an autonomous vehicle in accordance with an embodimentof the invention. The system 400 typically includes one or more inputdevices 202. An input device may be an operator input device thatdirects at least part of the vehicle (e.g., one or more of a steeringwheel, handle, brake pedal, accelerator, or throttle). The input devicealso may be a device directly or indirectly connecting the operatorinput device to a controlled element (i.e., the object in the autonomousvehicle ultimately controlled by the operator input device) For example,the input device can be a drive control 204. A drive control generallyincludes a throttle 206, brake 208, accelerator 210, or transmissionshifter 211, or any combination thereof. A typical input device 202 is athrottle body (not depicted), which is typically connected to thethrottle 206. Other example input devices 202 include a steering gear(not depicted) and tie rods (not depicted). In other embodiments, theinput device can include an articulation control 212.

The system 400 also includes one or more control policies 214corresponding to the input device 202. Generally, the control policy 214determines the manner in which the vehicle will operate, typicallyallowing for vehicle control under autonomous or manual conditions, or acombination thereof. The system 400 also includes one or more actuators216 associated with the one or more input devices 202. Typically, theactuator 216 includes an electro-mechanical device that drives the inputdevice 202. In one embodiment of the invention, the actuator 216includes one or more linkages or other mechanical transmissions 218.Generally, the linkage provides the association (e.g., physicalconnection) between an actuator 216 and the associated input device 202.A typical linkage is a lever and pivot joint, a typical transmission isa rack and pinion device. In one embodiment of the invention, thelinkage 218 manipulates an input device 202 in response to the safetysignal in accordance with the corresponding control policy 214.

The system 400 also includes one or more controllers 226 that, in someembodiments, are in communication with the actuators 216, the controlpolicy 214, and one or more sensors 402. Generally, the sensor 402includes any device that is capable of assessing the environment in andaround the vehicle for the presence or absence of hazards or obstacles,as well as the position, or orientation, or both, of the vehicle. Forexample, in some embodiments a sensor is a localization sensor, such asa pitch sensor, roll sensor, yaw sensor, inertial navigation system, acompass, a global positioning system, or an odometer. In otherembodiments, a sensor is a perception sensor, such as a LIDAR system,stereo vision system, infrared vision system, radar system, or sonarsystem. In some embodiments, the controller 226 transmits the safetysignal based at least in part on the control policies 214. In someembodiments, the controller 226 is a microprocessor. In otherembodiments, the controller 226 is a microcontroller.

A feature of the system 400 is that it includes a first communicationlink 406 between the controller 226 and each of the actuators 216. Inone embodiment of the invention, the first communication link 406includes a network connection. Another feature of the system 400 is thatit includes a second communication link 408 between each of theplurality of actuators 218. In one embodiment of the invention, thesecond communication link 408 includes at least one current loop. Inanother embodiment of the invention, the second communication link 408conveys a manual mode signal, an autonomous mode signal, or anycombination thereof. In an alternate embodiment of the invention, thesecond communication link 408 conveys a stop signal, a non-stop signal,or any combination thereof.

The system 400 also includes a transmitter 404 which, in someembodiments of the invention, transmits the safety signal to at leastone of the actuators 216 via the first communication link 406, thesecond communication link 408, or any combination thereof. Generally,the transmitter 404 can transmit data, such as the safety signal forexample, in any manner in which data is transmitted to the actuators216. For example, the transmission may be electrical, mechanical, wired,wireless, or any combination thereof. In some embodiments, the safetysignal is transmitted in response to operator intervention. In otherembodiments, the safety signal is transmitted in response to the outputof at least one of the sensors 402.

In brief overview, FIG. 5 is a flowchart depicting a method 500 fortracking at least one terrain feature by an autonomous vehicle inaccordance with an embodiment of the invention. The method includes astep of first providing one or more localization sensors (STEP 502). Thefusion of multiple localization sensors typically determines theposition of the vehicle relative to one or more reference points. Forexample, in some embodiments, the localization sensor suite includes apitch sensor, roll sensor, yaw sensor, compass, global positioningsystem, inertial navigation system, odometer, or any combinationthereof. By fusing the weighed values of all of these sensors together,a more accurate representation of the vehicle's position and orientationcan be achieved. For example, in some embodiments, data from the globalpositioning system, odometer, and compass may be fused together toaccurately determine the position of the vehicle.

Next, the method 500 includes the step of providing one or moreperception sensors (STEP 504). The perception sensor typically assessesthe environment about the vehicle. For example, in some embodiments, theperception sensor suite includes a LIDAR system, stereo vision, infraredvision, radar, sonar, or any combination thereof. The ranging andfeature data from the suite are fused together in a weighted fashion tobuild a more accurate representation of the space around the vehiclethan can be achieved by using any single sensor alone. Next, embodimentsaccording to the invention detect one or more terrain features about thevehicle (STEP 506). Detection is based at least in part on a change inthe output of the perception sensor. Generally, the perception sensorwill indicate the presence of a terrain feature that is a potentialdanger or hazard to the vehicle and that the vehicle may need to avoid.For example, the output of the perception sensor may indicate thepresence of one or more of a fence, rock, ditch, animal, person, steepincline or decline, or any combination thereof. For example, in someembodiments, this feature may be a dismounted infantry soldier that thevehicle may need to track to perform a simple autonomous mission likefollowing.

Next, the location of the terrain feature relative to the position ofthe vehicle is computed (STEP 508). The computation is based at least inpart on the output of the localization sensor. For example, the outputof the localization sensor is interpreted to place the vehicle at apoint of a coordinate system. The output of the perception sensor isinterpreted to place the terrain feature at particular coordinatesrelative to this point. Computations based on, for example, analyticgeometry determine the displacement (i.e., distance and direction)between the terrain feature and the vehicle. For example, for a tractortilling a field, the localization sensor of a tractor indicates thetractor is at point “A.” The perception sensor then indicates thepresence of a terrain feature, such as a fence. The location of thefence is then computed relative to point A. For example, the fence maybe computed as being 100 feet directly in front of the vehicle locationat point A. Of course, as the vehicle moves, point “A” moves as well. Asthe vehicle moves to a boundary of the coordinate system, the latter maybe expanded or redefined to encompass additional area where the vehiclemay traverse. In other words, the vehicle will not “fall off the map.”Alternatively, in some embodiments, the origin of the coordinate systemmay be defined as the instantaneous location of the vehicle, meaningthat the coordinate system can represent a roving sub-region of theuniverse about the vehicle. In this configuration, with the vehicle inmotion, terrain features can enter and leave the coordinate system asthey encounter the boundaries of the latter.

Next, the location(s) of the terrain feature(s) is (are) stored in atleast one memory (STEP 510). In some embodiments, a precisedetermination of a terrain feature's location is required so, forexample, the location data includes information to identify the terrainfeature's location in three dimensions. Nevertheless, this may require alarge amount of memory so, in some embodiments (e.g., where lessprecision is adequate), three-dimensional location data are mapped totwo dimensions and stored accordingly (STEP 512). This generally reducesthe amount of memory needed. In certain embodiments, terrain featuredata is stored as points within a two dimensional plane. For example, insome embodiments, the system observes the location of the point in threedimensional space. If the point is higher than the top of the vehicleplus a danger buffer zone, then the point is discarded. If the point iswithin the plane of the ground surface, then the point is discarded. Ifthe point is below the plane of the ground surface, it is retained as a“negative obstacle,” i.e., a lack of surface across which to run. If thepoint is within the z-altitude that the body of the vehicle could passthrough, it is stored as a “positive obstacle.” Locations with thetwo-dimensional space that do not have stored points are presumed to bepassable. In addition, terrain features may be stored as a point cloudset, whereby discarding three-dimensional points outside the volume ofinterest significantly reduces the size of the set. In the alternative,terrain feature data may be stored as bits within a two-dimensionaloccupancy grid, where the two-dimensional grid is smaller than athree-dimensional grid by the represented altitude divided by thevertical granularity. For example, in one embodiment, a boulder or otherobject or terrain feature may be detected at a location given byCartesian coordinates (x₁,y₁,z₁) relative to the location of the vehicle(defined as x₀,y₀,z₀). By storing only the x- and y-coordinates and notinvolving the z-coordinates in computations, memory is conserved andmathematical processing requirements are reduced. (In this example, thex- and y-coordinates represent the surface on which the vehicle travels,and the z-coordinate represents the elevation relative to this surface.Note that coordinate systems other than Cartesian (e.g., polar orspherical) may be used.)

Typically, the vehicle is in motion and the terrain feature isstationary. The scope of the invention also includes the case where thevehicle is stationary and the terrain feature is in motion, or the casewhere both the vehicle and terrain feature are in motion. In any case,an embodiment of the invention includes the step of updating the storedlocation of the terrain feature as its location changes relative to thevehicle (STEP 518). Consequently, the vehicle maintains an accurate anddynamic representation of the surrounding terrain and terrain feature.

In some embodiments, updating the stored location (STEP 518) includesrecomputing the location of the terrain feature based on changes in theoutputs of the localization sensors, perception sensors, or both (STEP524). Generally, once one of the sensors indicates a change from aprevious output, the location is recomputed (STEP 524) and stored inmemory, and thus the stored location is updated. In some embodiments,updating the stored location of the terrain feature (STEP 518) is basedonly on a change in the output of the localization sensor, indicating achange in the location of the vehicle. For example, the perceptionsensor may detect a stationary boulder while the vehicle is moving. Themovements of the vehicle cause changes in the output of the localizationsensor (i.e., the changing output represents the changing location ofthe vehicle). The outputs of the localization and perception sensors areused to compute a displacement to the terrain feature. Because thisdisplacement is relative to the location of the vehicle, and because thevehicle is moving, updated displacement values are computed during themovement.

In other embodiments, updating the stored location of the terrainfeature (STEP 518) is based only on a change in the output of theperception sensor, indicating a change in the environment about thevehicle, for example the initial detection of a terrain feature ormovement of a terrain feature. When the vehicle is stationary and theterrain feature is moving, changes in the output of the perceptionsensor give rise to changing displacement values.

In some embodiments, after recomputing the location of the terrainfeature (STEP 524), the previously stored location is discarded frommemory (STEP 522), typically to conserve space. In one embodiment, thediscard occurs after a predetermined condition is met (STEP 520). Atypical predetermined condition permits the discard when thedisplacement between the vehicle and the terrain feature exceeds aparticular value, generally because the terrain feature is too distantto represent a hazard to the vehicle. For example, if a boulder isdetected ten meters from the vehicle, but the vehicle is moving (asdetected by the localization sensor) away from the boulder, the computeddisplacement to the boulder will increase. When, for example, thedistance portion of the displacement exceeds fifteen meters, thelocation of the terrain feature is discarded.

In another embodiment, the perception sensor is characterized by apersistence. Generally, a persistence means that the perception sensormust assess the surrounding environment for a period of time beforeindicating the state of the surrounding environment. In other words, asingle detection, based on, for example, on one sweep of the surroundingenvironment by the perception sensors may, in some embodiments, beinsufficient for the perception sensor to indicate the presence of aterrain feature. Accordingly, in some embodiments, accurate detection ofa terrain feature requires multiple sweeps by the perception sensor, anddetection of that terrain feature on each sweep. Persistence addressesinstances where a terrain feature is intermittent and, therefore,unlikely to represent a hazard. For example, if a bird were to flyquickly in front of the perception sensor, then continue flying away andout of range of the perception sensor, the presence of the bird wouldnot be sensed as a terrain feature because the condition of thepersistence was not met, as the bird was detected in too few perceptionsensor sweeps of the environment about the vehicle.

If the perception sensor suite detects a terrain feature, the locationof the terrain feature is stored in memory as discussed above. If one ormore subsequent perception sensor sweeps fail to detect the terrainfeature, then, in some embodiments, a condition is met that causes thelocation of the terrain feature to be discarded. In other words, if aterrain feature does not “persist” in the field of view the perceptionsensors suite for a sufficient amount of time, then the terrain featureis deemed not to represent a hazard, and its location is discarded.

After the location of a terrain feature is determined, one embodimentincludes the step of adjusting the trajectory of the vehicle based atleast in part on the terrain feature location stored in the memory (STEP514). This is generally done to so the vehicle avoids the terrainfeatures that are obstacles and any attendant hazards. Adjustment in thetrajectory may be any change in the movement of the vehicle. In someembodiments, the step of adjusting the trajectory (STEP 514) includesthe step of selecting the preferred trajectory from a plurality ofranked alternative trajectories (STEP 516). Generally, the plurality ofalternative trajectories may be possible responses to a terrain feature,and they typically are ranked in a certain order that indicatespreference. For example, the most preferred alternative trajectory maybe that trajectory that requires the smallest adjustment to avoid acollision. Conversely, the least preferred alternative trajectory mayrequire the largest adjustment.

As an illustrative example, consider the case where a terrain feature isminor in nature, such as a small shrub that is computed to beseventy-five meters in front and two degrees to the left of the vehicle.The selected preferred response may be to adjust the vehicle trajectoryby moving one degree to the right causing the vehicle to continue closeto the terrain feature while avoiding a collision. Conversely, if theterrain feature is major, such as a cliff located thirty meters directlyin front of the vehicle for example, the preferred trajectory may be a180 degree change in vehicle direction.

FIG. 6 is a block diagram depicting a system 600 for tracking a terrainfeature by an autonomous vehicle in accordance with an embodiment of theinvention. The system 600 includes a localization sensor suite 602. Thelocalization sensor suite may include a pitch sensor 604, a roll sensor606, a yaw sensor 608, an inertial navigation system 610, a compass 612,a global positioning system 614, an odometer 616, or any combinationthereof. The localization sensor suite 602 generally includes any deviceor sensor capable at least in part of determining the position ororientation of the autonomous vehicle. The localization sensor suite 602fuses the data from each sensor in the suite together in a weightedfashion to achieve a more robust estimations of state than is availablewith any individual sensor by itself. In some embodiments, thelocalization sensor suite 602 determines the orientation of the vehicle,such as its pitch, roll, or yaw in part to ensure that the vehicle isnot in danger of tipping over on its side, for example. In otherembodiments, the localization sensor suite 602 determines the positionof the vehicle in addition to its orientation, such as the location ofthe vehicle on a plot of land, for example.

The system also includes a perception sensor suite 618. The perceptionsensor suite assesses the environment about the vehicle and generallyincludes a LIDAR system 620, stereo vision system 622, infrared visionsystem 624, a radar system 628 a sonar system 630, or any combinationthereof. The system 600 also includes a detector 220 that detects thepresence of all navigationally significant terrain features in responseto a change in the output of the perception sensor suite 618. Generally,the detector 220 is typically apparatus or software that correlates theoutput of the perception sensor suite 618 to the presence or absence ofa terrain feature.

In an alternative embodiment, the perception sensor suite 618 ischaracterized at least in part by a persistence. Generally, apersistence ensures against a false-positive reading of a potentialterrain feature by creating a condition that the terrain feature mustremain the perception sensor suite 618 field of view for a particulartime, typically for a number of perception sensor sweeps. For example,if a tractor is tilling a plot of land, in addition to permanent terrainfeatures such as, for example, trees, rocks, or fences, the perceptionsensor suite 618 combined with the detector 220 will also detect objectsthat briefly enter the environment about the vehicle including, forexample, a bird that flies across the field at a relatively lowaltitude, a ball that is thrown through the environment about thevehicle, debris carried by the wind through this same environment, orother transitory objects. In one embodiment, if a terrain feature doesnot “persist” in the perception sensor suite 618 field of view for aparticular time, then the terrain feature does not represent a hazard tothe vehicle. Typically, the persistence may be defined to increase ordecrease the likelihood that transitory objects, such as the examplesgiven above, are characterized and assessed as terrain features.

The system 600 also includes a controller 226 capable of computing thelocation of at least one terrain feature relative to the position of thevehicle and based at least in part on the output of the localizationsensor suite 602. In some embodiments, the controller 226 includes amicroprocessor. In other embodiments, the controller 226 includes amicrocontroller. Generally, once the detector 220 has detected a terrainfeature based at least in part on a change in perception sensor suite618 output, the controller 226, in communication with the detector 220,computes the distance to the terrain feature relative to the vehiclebased on the output of the localization sensor suite 602. For example,the presence of a fence on a plot of land causes a change in perceptionsensor suite 618 output, such that detector 220 detects the fence as aterrain feature. The localization sensor suite 602 output indicates thatthe vehicle is currently at a specific point on the same plot of land.The controller 226 then calculates the displacement between the vehicleand the fence.

The system 600 also includes a memory 632 for storing the location ofone or more terrain features. The memory can be volatile (e.g., SRAM,DRAM) or nonvolatile (e.g., ROM, FLASH, magnetic (disk), optical(disk)). In an alternative embodiment, the stored location of a terrainfeature in memory 632 includes a mapped two-dimensional representationof a three dimensional representation 634. Generally, in someembodiments, the mapped two-dimensional representation includes any twocoordinate points that identify the distance of a terrain featurerelative to the vehicle. The two-dimensional representation typicallyprovides less precision, but requires less memory and computationalpower to maintain or update. The reduced precision compared to athree-dimensional representation may be adequate in certainapplications.

In some embodiments, the stored location of a terrain feature is basedon a change in the output of the localization sensor suite 602.Generally, if a terrain feature is stationary but the vehicle is inmotion, the localization sensor suite 602 output changes to reflect themotion of the vehicle. The controller 226 then determines thedisplacement between the terrain feature and the new vehicle location,and this new displacement is stored in memory 632. Therefore, in thisembodiment, the stored location is based on a change in localizationsensor suite 602 output.

In other embodiments, the stored location of a terrain feature is basedon a change in the output of the perception sensor suite 618. Forexample, if a terrain feature such as a cow begins moving towards theoperating vehicle (e.g., a tractor), the perception sensor suite 618output will indicate this change in the environment about the vehicle.The detector 220 will detect this change in output and the controller226 will compute the location of the terrain feature relative to thevehicle. This new displacement will then be stored in memory 632 basedon the change in perception sensor suite 618 output caused, in thisexample, by the movement of the cow.

In an alternative embodiment, the system 600 also includes logic 636 fordiscarding the stored location based at least in part on satisfying atleast one predetermined condition. Generally, the predeterminedcondition may include any user-defined terms, events, or any combinationthereof that must occur or be in existence before discarding the terrainfeature's location from memory 632. In yet another embodiment, thepredetermined condition includes exceeding a predetermined displacementbetween the location of the terrain feature and the location of thevehicle. For example, in one possible embodiment, the system 600 is setwith a predetermined displacement value of fifteen meters rearward ofthe vehicle, a terrain feature is detected ten meters directly south ofthe vehicle, and the vehicle is moving north. The location of thisterrain feature is stored in memory because it is within (i.e., closerto the vehicle than) the fifteen meter rearward predetermineddisplacement. Continuing with the example, as time progresses, thevehicle moves such that the terrain feature is over fifteen metersbehind the vehicle. At this point, the location of the terrain featurewill, in this embodiment, be deleted from memory 632 and not be storedin memory 632 unless the object once again comes within thepredetermined displacement value.

In yet another embodiment, the logic 636 discards the stored locationwhen the predetermined condition includes failing to detect continuouslythe terrain feature for a sufficient amount of time (e.g., the terrainfeature does not “persist” in the field of view the perception sensorsfor a sufficient number of sweeps). For example, the predeterminedcondition may be that the perception sensor suite 618 indicates that aterrain feature is greater than a certain distance, for example fiftymeters, from the vehicle, and the persistence generally ensures that theperception sensor suite 618 repeatedly over a period of time sweepsthrough the environment about the vehicle, senses the presence of theterrain feature. In such a case, a single indication that the terrainfeature that was once forty-nine meters from the vehicle is now morethan fifty meters from the vehicle may be insufficient to cause thestored location to be discarded from memory 632 because the persistencehas not been satisfied. However, multiple indications over a period oftime, or multiple sweeps by the perception sensor suite 618 that allindicate that the terrain feature may satisfy the predeterminedcondition, (i.e., is greater than fifty meters from the vehicle) and mayalso satisfy the persistence, therefore in this case the terrain featurelocation will be discarded from memory 632.

In another embodiment, the system 600 includes adjustment logic 638 foradjusting the trajectory of the vehicle based at least in part on thelocation of one or more terrain features stored in memory 632.Generally, adjustment logic 638 may alter the direction or trajectory ofthe vehicle and may include any change in the vehicle direction, mode ofoperation, or any combination thereof. For example, if a terrain featureis stored in memory 632 as being twenty meters in front of the vehicle,the adjustment logic 638 may adjust the vehicle trajectory to the leftby five degrees, resulting in the avoidance of a collision between theterrain feature and the vehicle. In some embodiments, the adjustmentlogic 638 includes a selector 640 for selecting one preferred trajectoryfrom a plurality of ranked alternative trajectories. To continue withthe immediately preceding example, in response to a terrain featuretwenty meters in front of the vehicle, the selector may for example havethe options of entering a controlled shutdown, turning left fivedegrees, left ten degrees, right five degrees, right ten degrees, orturning around 180 degrees. In one embodiment, the alternativetrajectory of turning the vehicle to the left five degrees may be themost desirable and thus highest ranked of all alternative trajectories.Therefore, the selector 640 selects this option to be executed by thevehicle.

In brief overview, FIG. 7 is a flowchart depicting a method 700 forbehavior based control of a vehicle in accordance with an embodiment ofthe invention. The method includes the step of first identifying one ormore input devices in the vehicle (STEP 104). An input device may be anoperator input device that directs at least part of the vehicle (e.g.,one or more of a steering wheel, handle, brake pedal, accelerator, orthrottle). The input device also may be a device directly or indirectlyconnecting the operator input device to a controlled element (i.e., theobject in the autonomous vehicle ultimately controlled by the operatorinput device). For example, the input device can be a drive control. Adrive control generally includes a throttle, brake, accelerator, or anycombination thereof. A typical input device is a throttle body, which istypically connected to the throttle 206. Other example input devicesinclude a steering gear and tie rods. In other embodiments, the inputdevice can be an articulation control. An articulation control generallyoperates equipment attached to the vehicle. This can include, forexample, a control used to manipulate a blade on a bulldozer, or atilling apparatus on a tractor.

Next, the method 700 includes the step of providing one or moreactuators (STEP 108) associated with one or more input devices. Theactuator is typically an electro-mechanical device that manipulates theinput devices. Manipulation occurs by, for example, pushing, pulling, orturning the input devices, or by any combination thereof. A result ofthis is the autonomous control of the vehicle. Generally, the presenceof actuators in the vehicle does not preclude manual operation of thecorresponding input devices.

In addition to the step of identifying the input devices(STEP 104), andproviding the actuators (STEP 108) the invention also includes the stepof defining a plurality of operational modes (STEP 702) associated withthe actuators. Each mode allows the vehicle to be operated in a separateand distinct fashion. Each mode may also include a plurality ofbehaviors. Each behavior typically is a separate program that proposesan action set to the vehicle's behavior arbiter. In some embodiments,the step of defining a plurality of operational modes (STEP 702)includes defining a manned operation mode (STEP 704), a remote unmannedtele-operation mode (STEP 706), an assisted remote tele-operation mode(STEP 708), an autonomous unmanned operation mode (STEP 710), or anycombination thereof. Autonomous unmanned operation mode (STEP 710) isthe state where the vehicle is performing a prescribed task with littleor no operator intervention. The vehicle modifies its actions tocompensate for terrain features that may be obstacles and other hazards.In contrast, the manned operation mode (STEP 704) overrides autonomouscontrol of the vehicle and allows an operator to control the vehicle.The two tele-operational modes (STEP 706 and STEP 708) are the stateswhere the unmanned vehicle is being operated from a remote location by adismounted operator or by an operator in a chase vehicle.

Next, some embodiments of the invention include the step of defining atleast one action set (STEP 711). An action set is typicallycharacterized at least in part by a priority and each action setgenerally includes a plurality of alternative actions that are rankedaccording to a corresponding plurality of preferences.

Next, in an embodiment of the invention, an arbiter or arbiters that areassociated with the actuator are provided (STEP 714). An arbiter selectsthe action set having the highest corresponding priority (STEP 713). Thearbiter also selects the alternative action from the selected action sethaving the highest preference (STEP 712). In some embodiments, theselection of the alternative action (STEP 712) includes the selection ofa trajectory set (STEP 716). A trajectory set is typically a series ofalternative navigation commands that prescribe the vehicle direction andrate of travel (i.e., translational and rotational velocity). Forexample, to avoid a terrain feature or other hazard, the vehicle maychange its speed, direction, or both, in varying degrees. To accomplishthis, the vehicle may slow slightly and turn slightly, or it may turnabruptly and slow dramatically (e.g., to maintain vehicle stability).Clearly, many combinations of speed and direction are possible.Generally, each such combination is a member of the trajectory set.

Next, in some embodiments, the arbiter modifies the selected action set(STEP 718), typically by modifying one or more of the alternativeactions contained in the selected action set. Modification generallyentails tailoring the chosen action to the particular situation suchthat the vehicle then executes the modified chosen action. For example,for the selected trajectory set, the arbiter can reduce the vehiclevelocity along the arc of travel. To illustrate, consider the case wherea tractor is tilling a field under autonomous operation. Assume that anobstacle, such as a tree, is detected in the path of the tractor, butstill at a safe distance ahead of the tractor. At this point, there areseveral potential behaviors available to the vehicle. Some of thepossibilities include for the tractor to remain in autonomous operation,or switch to manual operation or safety operation. Staying with thisrepresentative example, it is typically within the ability of thetractor to avoid a static object, such as a tree, while in autonomouscontrol. In this example, the arbiter examines the available alternativeaction sets (i.e., alternative trajectory sets that will keep thetractor from encountering the tree). The arbiter then selects thehighest priority action set (e.g., the trajectory set requiring theleast amount of change relative to the intended path of the vehicle).

In some embodiments, the arbiter modifies the selected action set (STEP718), typically in response to other data. The data may includeinformation received from sensors (STEP 720), such as the localizationsensor suite 602, or the perception sensor suite 618, or both. In someembodiments, the data may include a constraint on actions. Thisconstraint may include a command that the selected trajectory set notallow vehicle movement in a certain direction, or at a certain speed. Insome embodiments, the selected action set may include a restriction setfor implementing the constraint on the action set. Generally, theconstraint defines an impermissible area of vehicle operation. The datamay also include information received from the vehicle's resident localterrain feature map (STEP 722). In other words, the selected trajectoryset provides a baseline alternative trajectory for the vehicle, butarbiter can modify this baseline to compensate for variations in theenvironment around the vehicle. While the baseline trajectory may beadequate in some circumstances, the presence of, for example, otherterrain features or hazards along the baseline trajectory is generallyunacceptable. The arbiter integrates information received from sensorsand map data to ensure that the vehicle can adhere to baselinetrajectory without significant risk. If the vehicle were to encounterterrain features or hazards along the baseline trajectory, the arbitermodifies the latter as needed.

In some embodiments, after the alternative action with the highestpreference has been selected, an embodiment of the invention operatesthe input device in accordance with the selected alternative action(STEP 726). In some embodiments, the action set may be modified (STEP718) before operating the input device in accordance with the selectedalternative action (STEP 726). Generally, once the arbiter has selectedan alternative action (STEP 712) from the selected action set andmodified (STEP 718) the selected action set, the input device is thenoperated in accordance with that action. For example, if the selectedalternative action is a safety operation, such as a controlled shutdownof the tilling apparatus on a tractor, and the arbiter modifies thisalternative action by allowing background operations, such as thelocalization sensors to continue running, the input device associatedwith the tilling apparatus will be commanded to shut down, but thelocalization sensors will continue to operate normally in a mannerconsistent with the selected alternative action.

FIG. 8 is a block diagram depicting a system 800 for behavior basedcontrol of a vehicle in accordance with an embodiment of the invention.As in the other Figures, the interconnections depicted in FIG. 8represent various communication paths between the enumerated objects.The system 800 typically includes one or more input devices 202. Aninput device may be an operator input device that directs at least partof the vehicle (e.g., one or more of a steering wheel, handle, brakepedal, accelerator, or throttle). The input device also may be a devicedirectly or indirectly connecting the operator input device to acontrolled element (i.e., the object in the autonomous vehicleultimately controlled by the operator input device). For example, theinput device can be a drive control 204. A drive control generallyincludes a throttle 206, brake 208, accelerator 210, or transmissionshifter 211, or any combination thereof. A typical input device 202 is athrottle body (not depicted), which is typically connected to thethrottle 206. Other example input devices 202 include a steering gear(not depicted) and tie rods (not depicted). In other embodiments, theinput device includes an articulation control 212.

The system 800 also includes one or more actuators 216 associated withthe one or more input devices 202. Typically, the actuator 216 includesan electro-mechanical device that drives the input device 202. In oneembodiment of the invention, the actuator 216 includes one or morelinkages or other mechanical transmissions 218. Generally, a linkageprovides the association, (e.g., physical connection) between anactuator 216 and the associated input device 202. A typical linkage is alever and pivot joint, a typical transmission is a rack and piniondevice.

The system 800 also includes a plurality of behaviors 802 associatedwith the actuator 216, where each behavior 802 includes at least oneaction set 805 ranked according to a corresponding plurality ofpriorities, and each action set 805 includes a plurality of alternativeactions 804 ranked according to a corresponding plurality ofpreferences. The system 800 also includes at least one arbiter 816associated with the actuator 216 for selecting the action set 805 havingthe highest corresponding priority and for selecting the alternativeaction 804 having the highest corresponding preference within theselected action set 805. In some embodiments the arbiter 816 modifiesthe selected alternative action 804. Generally, the arbiter is software,hardware, or a combination thereof.

The different modes of vehicle operation generally contain a pluralityof behaviors. For example, in some embodiments, the modes include aremote unmanned tele-operation mode 806, a manned operation mode 808, anautonomous unmanned operation mode 810, assisted remote tele-operationmode 812, or any combination thereof. These modes each generallycorrespond to different vehicle missions. For example, the mannedoperation mode 808 may dictate that only the operator may control thevehicle, whereas autonomous unmanned operation mode 810 would generallybe a behavior where the vehicle needs little or no operatorintervention. The remote unmanned tele-operation mode 806 and assistedremote tele-operations mode 812 are the states where the unmannedvehicle is being operated from a remote location by a dismountedoperator or by an operator in a chase vehicle. In some embodiments, theplurality of alternative actions 804 of an action set 805 include atrajectory set 814. Generally, the trajectory set 814 includes aplurality of possible trajectories, or paths, that the vehicle mayfollow. For example, a trajectory set 814 represents the possible pathsof vehicle motion with each path being one degree clockwise from theprevious trajectory path. In some embodiments, the vehicle modifies theselected action to avoid a terrain feature.

Additionally, in some embodiments, the system 800 may include at leastone adjuster 820 for adjusting the translational velocity of the vehicleand a rotational velocity of the vehicle, or any combination thereof.Generally, the adjuster 820 will adjust the speed, or direction, orboth, of the vehicle so it follows its designated trajectory or avoidsan obstacle.

A plurality of priorities determines the ranking of the plurality ofalternative actions. Generally, the most important actions for safevehicle operation will be given the highest priority. For example, ifthere is a boulder 100 meters in front of the vehicle, and a group ofpeople five yards in front of the vehicle, within an action set 805there will be one alternative action 804 for avoiding the boulder, forexample a slight adjustment in the vehicle rotational velocity, whichwould be an autonomous unmanned operation 810, appropriately modified.There may be another alternative action 804 for avoiding the group ofpeople, for example a controlled emergency shutdown. Here, from withinaction set 805 the alternative action 804 with the highest correspondingpreference would be given to the safety operation due to the moreimmediate nature of the threat. The priority can for example bedetermined from the distance to the terrain feature(s).

The maximum vehicle speed and correspondingly its maximum decelerationspeed can be linked to the amount and density of navigationallysignificant terrain features in the local vicinity of the vehicle. Thevehicle will limit its speed so it only requires a configurable fractionof the maximum deceleration rate of the vehicle to come to a completestop while still safely avoiding all obstacles. The planned fraction ofthe deceleration rate is typically used to control the fraction of thevehicle's performance envelope used when avoiding obstacles. Thisprovides a configuration for providing safety margins and for tuning thesmoothness of the control of the vehicle.

The system 800 also includes one or more controllers 226 that, in someembodiments, are in communication with the input devices 202 and thearbiter 816 so the controller 226 operates the input devices 202 inaccordance with the selected alternative action 804. In some embodimentsthe selected alternative action 804 may be modified. In someembodiments, the controller 226 is a microprocessor. In otherembodiments, the controller 226 is a microcontroller. For example, ifthe alternative action 804 selected by the arbiter 816 calls for thevehicle to maintain autonomous operation while decreasing its speed byten percent and turning left by forty-five degrees, the controller 226will control the actuators 216 associated with the input devices 202,such as the drive control 204 to change the vehicle speed, and asteering wheel to change the vehicle direction.

In some embodiments of the invention, the system 800 also includes alocalization sensor suite 602, a perception sensor suite 618, a localvehicle centric terrain map 818, or any combination thereof. Typically,the localization sensor suite 602 may include one or more of a pitchsensor 604, roll sensor 606 yaw sensor 608, inertial navigation system610, compass 612, global positioning system 614, odometer 616, or anycombination thereof. The localization sensor suite 602 is generallyresponsible for fusing the data from multiple sensors together in aweighted fashion to develop a superior estimate of the position of thevehicle. Typically, the perception sensor suite 618 may include one ormore of a LIDAR system 620, stereo vision system 622, infrared visionsystem 624, radar system 628, sonar system 630, or any combinationthereof. The perception sensor suite 618 typically assesses theenvironment about the vehicle and is generally responsible for fusingthe data from multiple perception sensors together in a weighted fashionto develop a more accurate description of the navigationally significantterrain features in the local environment about the vehicle. The terrainmap 818 generally is a compilation of all terrain features detectedwithin the environment about the vehicle. For example, the terrain map818 may indicate that there is a steep incline twenty meters directly tothe left of the vehicle, and a tree 100 meters in front by twenty metersto the right of the vehicle.

In brief overview, FIG. 9 is a flowchart depicting a method 900 forselective control of a vehicle in accordance with an embodiment of theinvention. The method includes a step of identifying one or more inputdevices in the vehicle (STEP 104). An input device may be an operatorinput device that directs at least part of the vehicle (e.g., one ormore of a steering wheel, handle, brake pedal, accelerator, orthrottle). The input device also may be a device directly or indirectlyconnecting the operator input device to a controlled element (i.e., theobject in the autonomous vehicle ultimately controlled by the operatorinput device). For example, the input device can be a drive control. Adrive control generally includes a throttle, brake, or accelerator, orany combination thereof. A typical input device is a throttle body,which is typically connected to the throttle. Other example inputdevices include a steering gear and tie rods. In other embodiments, theinput device can be an articulation control. An articulation controlgenerally operates equipment attached to the vehicle. This can include,for example, a control used to manipulate a blade on a bulldozer, or atilling apparatus on a tractor.

In addition to the identification of the input devices (STEP 104), theinvention also includes the step of providing one or more actuators(STEP 108) associated with one or more input devices. The actuator istypically an electro-mechanical device that manipulates the inputdevice. Manipulation occurs by, for example, pushing, pulling, orturning the input device, or by any combination thereof. A result ofthis is the autonomous control of the vehicle. Furthermore, in anembodiment of the invention, the actuators still allow manual operationof the vehicle. In other words, the presence of actuators in the vehicledoes not preclude manual operation of the corresponding input devices.In some embodiments, a linkage or other mechanical transmissionassociates the actuator with the corresponding control surface. Alinkage is generally any apparatus that facilitates any connectionbetween the input device and the actuator. A typical linkage is a leverand pivot joint, a typical transmission is a rack and pinion device.

Next, a plurality of operational modes associated with the actuator aredefined (STEP 702). Generally, these operational modes may be defined toinclude manned operation (STEP 704), remote unmanned tele-operation(STEP 706), assisted remote tele-operation (STEP 708), autonomousunmanned operation (STEP 710), or any combination thereof.

Next, the vehicle receives at least one mode select command (STEP 902).Generally, the mode select commands dictate the operation of thevehicle. In some embodiments, this includes receiving an autonomousoperation command (STEP 912). In this case, the actuator manipulates theinput device (STEP 314) in accordance with (i) the task the vehicle isperforming, and (ii) at least one of the associated behaviors.

In another embodiment, receiving the mode select command (STEP 902)includes receiving a remote command (STEP 914). Generally, this allowsfor remote-controlled operation of the vehicle, i.e., the case where anoperator maintains control over the vehicle when not physically presentin the vehicle. Here, vehicle control typically is not autonomous, butthere is generally no disassociation between the actuators and the inputdevices because the association is usually necessary for remote vehicleoperation.

In another embodiment, receiving the mode select command (STEP 902)includes receiving a manual operation command (STEP 904). In this case,the step of manipulating the input device (STEP 314) may include thestep of disassociating the actuator from the input device (STEP 906).For example, after receiving of the manual operation command (STEP 904),the actuator typically decouples from the corresponding drive control.This allows an operator to work the drive control without resistancefrom the actuator. In other embodiments, after disassociating theactuator (STEP 906), the actuator is reassociated with the input device(STEP 908). For example, this may occur when a vehicle operatingmanually (i.e., with a disassociated actuator) reverts to autonomouscontrol. In such a case, the actuator must reassociate with the inputdevice to resume autonomous control of the input device. In an anotherembodiment, the step of reassociating the actuator (STEP 908) occursafter a predetermined delay (STEP 910). For example, such a delay can beimplemented as a safety precaution to ensure that the vehicle does notrevert prematurely or falsely to autonomous control.

In yet another embodiment, receiving the mode select command (STEP 902)includes receiving a semi-autonomous command (STEP 916). In this case,the step of manipulating the input device (STEP 314) includes operatingthe input device in accordance with (i) one or more of the plurality ofbehaviors, and (ii) at least one remote transmission. Generally, thesemi-autonomous command (STEP 916) allows autonomous operation ofcertain features of the vehicle in combination with operator control ofother features. The operator is typically, although not necessarily,located away from the vehicle. For example, a tractor may follow a pathor pattern prescribed and controlled by an operator. During traversal ofthe path or pattern, the tractor may encounter one or more terrainfeatures that are obstacles. It is likely that the operator would notsee these terrain features if the operator is not present in thevehicle. Consequently, it is advantageous that the vehicle compensatefor the presence of the terrain features without requiring operatorintervention. The vehicle accomplishes this by relying on an obstacleavoidance behavior that runs in concert with the semi-autonomous commandmode. The vehicle may, for example, autonomously alter its trajectory,or speed, or both to avoid the terrain features.

FIG. 10 is a block diagram that depicts a system 1000 for selectivecontrol of a vehicle in accordance with an embodiment of the invention.The system 1000 typically includes one or more input devices 202. Aninput device may be an operator input device that directs at least partof the vehicle (e.g., one or more of a steering wheel, handle, brakepedal, accelerator, or throttle). The input device also may be a devicedirectly or indirectly connecting the operator input device to acontrolled element (i.e., the object in the autonomous vehicleultimately controlled by the operator input device). For example, thecontrol surface can be a drive control 204. A drive control generallyincludes a throttle 206, brake 208, accelerator 210, transmissionshifter 211, or any combination thereof. A typical input device 202 is athrottle body (not depicted), which is typically connected to thethrottle 206. Other example input devices 202 include a steering gear(not depicted) and tie rods (not depicted). In other embodiments, theinput device can include an articulation control 212.

The system 1000 also includes one or more actuators 216 associated withthe input devices 202. Typically, the actuator 216 includes anelectro-mechanical device that drives the input device 202. In oneembodiment of the invention, the actuator 216 includes one or morelinkages or other mechanical transmissions 218. Generally, a linkageprovides the association (e.g., physical connection) between an actuator216 and the associated input device 202. A typical linkage is a leverand pivot joint, a typical transmission is a rack and pinion device.

The system 1000 also includes a plurality of behaviors 802 associatedwith the actuator 216. Generally, the behaviors are specific programsthat propose an action to an arbiter. The vehicles resident arbiter(s)decide(s) which behavior is expressed based on mission priorities andsensor data. Each behavior 802 typically represents a specificrecognizable action the vehicle might take. In some embodiments, thebehaviors 802 include terrain feature avoidance 1002. The behaviors 802and the terrain feature avoidance 1002 are typically software routines,but they may also include hardware configured to perform the requiredtask.

In some embodiments, the system 1000 also includes are least onereceiver 1004 for receiving at least one mode select command and atleast one controller 226 in communication with the receiver 1004. Thecontroller 226 executes a vehicle program 228 in accordance with theoperator commands. For example, if the command is to enter a controlledemergency shutdown, the receiver 1004 passes this command to thecontroller 226. The controller 226 executes the vehicle program 228 thatshuts down the vehicle. In some embodiments, the command may include amanual operation command that allows an operator to assume control ofthe vehicle. In this case, the vehicle control program includes aninhibitor 234 for disassociating the actuator 216 from the input device202, thereby freeing the latter for operator control. Generally, in someembodiments, the inhibitor prohibits resassociation of the actuator 216with the input device 202 to ensure that the system remains under manualcontrol. In other embodiments, the vehicle control program 228 includesa predetermined time delay 232. Generally, the time delay preventspremature changes from one mode of operation to another. For example,the operator may relinquish manual control to allow the reestablishmentof autonomous control. The reestablishment may be substantiallyinstantaneous or occur after the predetermined delay. This delay helpsprevent a premature or false return to autonomous control.

In other embodiments, the operator command may include an autonomousoperation command, or a semi-autonomous operation command, or both. Ineach case, the vehicle control program 228 includes a vehicle controlmodule 1006 that, in cooperation with the controller 226, providesinstructions that control vehicle operation. The vehicle control module1006 typically includes one or more software routines, but it may alsoinclude hardware configured to control the vehicle. In particular, thevehicle control module 1006 typically communicates with the receiver1004 to receive commands sent to the vehicle. These received commandsare typically remote transmissions, e.g., sent by an operator who is notin the vehicle. After receiving the semi-autonomous operation command,the vehicle control module 1006 typically allows the manual operation ofvehicle input devices, features, or functions, but retains theautonomous control of certain aspects of the vehicle. For example, atractor may have its speed and direction controlled via remotetransmission. If an terrain feature that is an obstacle arises in thepath of the vehicle, the vehicle compensates for the presence of theobstacle without requiring operator intervention, typically by relyingon an obstacle avoidance behavior that runs in concert with thesemi-autonomous mode.

Note that in FIGS. 1 through 10 the enumerated items are shown asindividual elements. In actual implementations of the invention,however, they may be inseparable components of other electronic devicessuch as a digital computer. Thus, actions described above may beimplemented in software that may be embodied in an article ofmanufacture that includes a program storage medium. The program storagemedium includes data signals embodied in one or more of a carrier wave,a computer disk (magnetic, or optical (e.g., CD or DVD), or both),non-volatile memory, tape, a system memory, and a computer hard drive.

From the foregoing, it will be appreciated that the systems and methodsprovided by the invention afford a simple and effective way to safelycontrol a vehicle so the vehicle performs its predetermined tasks suchas for example removing an operator from harm's way during a dangerousapplication, or for example to offer direct labor costs savings incommercial applications, in an efficient manner.

One skilled in the art will realize the invention may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. The foregoing embodiments are therefore to beconsidered in all respects illustrative rather than limiting of theinvention described herein. Scope of the invention is thus indicated bythe appended claims, rather than by the foregoing description, and allchanges that come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

1-28. (canceled)
 29. A vehicle capable of manned operation, the vehiclecomprising: (a) a first subsystem, comprising: a computing medium havingcomputer readable code embodied therein for selectively controlling thevehicle, the computer readable code comprising: (i) code for enablingthe vehicle to be remotely controlled by an operator not physicallypresent in the vehicle; (ii) code for causing the vehicle to beautonomously controlled without operator intervention; and (iii) codefor enabling autonomous operation of a first vehicle feature incombination with operator control of a second vehicle feature; and (b) asecond subsystem in electrical communication with the first subsystem,the second subsystem comprising: at least one actuator for manipulatingone or more devices of the vehicle; and a controller for controlling atleast one such actuator in response to an instruction received from thecomputing medium.
 30. The vehicle of claim 29, wherein the computingmedium comprises code for causing the vehicle to automatically travelthrough a pre-recorded set of fixed waypoints.
 31. The vehicle of claim29, wherein the controller controls the at least one actuator so as tocause the vehicle to automatically travel through a pre-recorded set offixed waypoints.
 32. The vehicle of claim 29, wherein the computingmedium comprises code for causing the vehicle to automatically follow amoving object.
 33. The vehicle of claim 29, wherein the controllercontrols the at least one actuator so as to cause the vehicle toautomatically follow a moving object.
 34. The vehicle of claim 29,wherein the computing medium comprises code for causing the vehicle toautomatically avoid an obstacle.
 35. The vehicle of claim 29, whereinthe controller controls the at least one actuator so as to cause thevehicle to automatically avoid an obstacle.
 36. The vehicle of claim 29,wherein the computing medium further comprises code for overridingautonomous control of the vehicle in favor of manual operator control ofthe vehicle.
 37. The vehicle of claim 29 further comprising at least onesensor for assessing an environment in and around the vehicle.
 38. Thevehicle of claim 29 further comprising a global positioning system, aLIDAR system, an inertial navigation system, and an odometer.
 39. Thevehicle of claim 29, wherein the at least one actuator manipulates avehicle device selected from the group consisting of a steering gear, athrottle, a brake, and a transmission.
 40. The vehicle of claim 29,wherein at least one such actuator is coupled to a device of the vehicleby a mechanical linkage or a mechanical transmission.
 41. The vehicle ofclaim 40, wherein the mechanical linkage comprises a lever and a pivotjoint.
 42. The vehicle of claim 40, wherein the mechanical transmissioncomprises a rack and pinion device.
 43. The vehicle of claim 29 furthercomprising an emergency stop button for shutting down the vehicle.